Non-conjoined lumens arise in a variety of settings including surgical settings where the non-conjoined lumens are intentionally created or those arising from lacerations or puncture wounds. Intentionally created non-conjoined lumens include those arising during surgical repair of e.g., treatment of a blockage in a lumen by bypass procedures, attaching a synthetic graft or during free tissue transfer in cosmetic surgical settings. Anastomosis is conducted to surgically reconnect the open ends of the lumen. Examples of anastomosis procedures include anastomotic procedures on the vasculature, the vas deferens, the fallopian tubes, the urinary tract, tear ducts, bowel, mammary glands, alimentary ducts, pancreatic ducts, bile ducts, etc. In each case, the anastomosis procedure creates a channel for the flow of a body fluid there through.
The anastomosis may, for example, be end-to-end, end-to-side, and side-to-side. As is apparent from their names, anastomosis may involve various configurations. For instance, one tubular tissue may be joined side-to-end with two tubular tissues, creating a three-channeled tubular tissue construct.
In the surgical context, end-to-end anastomosis, as is apparent from its name, is a surgical procedure for connecting an end or distal portion of one tubular tissue structure to an end or distal portion of another tubular tissue structure, such that a continuous lumen is created. (As used herein, “end” or “distal portion”, refers to the open end of the tubular tissue).
In an end-to-side anastomosis, a tubular tissue structure having a hole or open part is connected through the open part to an open or distal end of a tubular tissue to form a continuous lumen with a branched configuration. Similarly, in a side-to-side anastomosis, two non-conjoined lumens are merged together into a continuous lumen though a hole or opening on each of the lumens to be joined.
A successful anastomosis typically involves the smooth connection of lumens, such that the internal structure is not blocked and internal body fluid flow—such as blood, semen or food or gastrointestinal fluids—is restored or improved. Ideally, the matching up/ligation surgical procedure is rapid and precise, so that patient exposure while in a vulnerable state—such as having blood flow stopped—is minimized.
There are a variety of “tubular tissues”, and the lumen of the first tubular tissue may not be of the same diameter as the lumen of the second tubular tissue. Thus, because the delicate surgery may involve matching and ligating two (or more) non-identical tubular tissues, various ligation techniques have been used with varying rates of success. These include sutures, tissue adhesives, adhesive strips, and staples, clips and other devices. To some extent all of these materials involve the skill of the practitioner in anastomosis which is accurate, durable and free from conditions which could cause latent deleterious reactions in vivo.
The labor-intensive needle and thread remains the most-used technology as of the present day. Because of the complexity and judgment required in suturing, automated techniques are not well accepted. Calcified and diseased vessels provide mechanical challenges. Sutures may, in some instances, cause a reaction resulting in long term stenosis or fibrosis.
Other approaches to anastomosis include the use of sealants and bioglues for ligation. These may be used individually or in conjunction with suturing or other mechanical ligation techniques or devices. For example, one commercially available sealant CoSeal® (Angiotech Pharmaceuticals, Inc., Vancouver, B.C., CA) may complement suturing in cardiovascular surgeries.
Mechanical anastomosis devices, such as clips, are also available. One commercially available device, the U-Clip™ (Medtronic, Minneapolis, Minn. 55432 USA), essentially provides a sharp, nitinol hook for knotting to compete anastomosis. The nitinol allows reversible deformation. The C-Port® (Cardica, Inc. Redwood City, Calif. 94063 USA) and related products are commercially available and use miniature stainless steel staples to securely attach the bypass graft to the coronary artery.
But, before ligating end-to-end (for example), the practitioner must match up the lumens by the circumference of the vessel (using blood vessels as an illustration). Frequently, this is troublesome to the practitioner because the end of an tubular tissue—such as a clamped blood vessel devoid of blood—is not a perfectly round circle; rather it is in its unpressurized, deflated-looking state where a cross-sectional view of the circumference may be a circle, an oval or irregular, and, of course having no structural support from within, is unstably in any shape (unless the surrounding tissue possesses structural strength). The size of the vessels to be so connected may be different. Although blood vessels (for example) or other tubular tissues are somewhat elastic (deformable and returning to the original shape) or plastic (deforming, and not fully returning to the original shape), connecting the circumferences of the lumens such that upon ligation there is no or minimal leakage (in the vascular context, for example), requires a skilled practitioner.
In a microvascular context, anastomosis is performed between ends of blood vessels in the course of, for example, reattaching severed body parts or transplanting organs. Microvascular anastomosis is often performed by hand under a microscope, and is tedious and painstaking work. The blood vessels connected together often have different diameters, both of which are very small, on the order of about 1 to about 5 millimeters (“mm”). Although blood vessels are usually at least somewhat elastic, the practitioner must match up end to end (for example) two different shaped-different-sized circumferences and then stitch them together (for example). As a result, it can take many hours to complete just the microvascular anastomosis required to reconnect a severed body part or transplant an organ.
One attempt to provide a mechanism for performing such a microvascular anastomosis is the Microvascular Anastomotic Coupler System, available from Bio-Vascular, Inc. (San Diego, Calif., USA). In this mechanism, an end of each vessel to be connected is essentially turned outward (“everted”) over a ring with a forceps or similar instrument. Each ring includes a number of pins over which the vessel is everted. The rings are then pressed together, such that the pins on each ring enter recesses in the other ring, connecting the rings and holding the ends of the vessels together. This system, however, is limited to use with two blood vessels having substantially the same diameter. Further, manual eversion of a blood vessel having a diameter on the order of one millimeter is difficult and painstaking, particularly when the eversion is to be substantially even around the circumference of the ring. Further, the rings provide a noncompliant anastomosis between the two vessels. Thus, although stabilizing the circumference facilitates the ability of the practitioner to match up vessels for end-to-end microvascular anastomosis, the device requires, essentially, practitioners skilled in microsurgical techniques.
For patients and practitioners, perhaps the most demanding anastomosis is incident to heart revascularization. The arteries that bring blood to the heart muscle (coronary arteries) can become clogged by plaque (a buildup of fat, cholesterol and other substances). This can slow or stop blood flow through the heart's blood vessels, leading to chest pain or a heart attack. Increasing blood flow to the heart muscle can relieve chest pain and reduce the risk of heart attack. A patient may undergo one, two, three or more bypass grafts, depending on how many coronary arteries are blocked.
Coronary artery bypass graft surgery (“CABG”, sometimes pronounced “cabbage” by practitioners) reroutes, or “bypasses,” blood around clogged arteries to improve blood flow and oxygen to the heart. In performing the CABG anastomosis, a segment of a healthy blood vessel from another part of the body is used to make a detour around the blocked part of the coronary artery. This healthy blood vessel may be, for example, an artery present in the thoracic cavity, or may be a piece of a long vein from the patient's leg. In some circumstances, grafts from non-autologous sources may be used, such as synthetic tubular tissues or animal tubular tissues. Regardless of the source of the healthy blood vessel, one end is connected to the large artery leaving the patient's heart (the aorta), and the other end is attached or “grafted” to the coronary artery below the blocked area. In this way of “rewiring” the vasculature, substantially unobstructed blood flow to the heart muscle is resumed.
Conventionally, a pump oxygenator (heart-lung machine) is used for coronary bypass graft operations. Medicines are used to stop the patient's heart, which allows the practitioner to operate without the heart beating. The heart-lung machine keeps oxygen-rich blood moving throughout the patient's body. For this conventional heart bypass graft surgery, a team of practitioners is needed (a surgeon, cardiac anesthesiologist and surgical nurse, and a perfusionist (blood flow specialist)). Multiple practitioners, additional complexity, and, as a practical matter, additional health care cost is involved over surgical procedures involving fewer practitioners and procedures.
Moreover, blood quality may be degraded as the heart-lung machine repetitively pumps the patient's blood through the systemic circulation. The blood may embolize or clot in the distal circulation, or form clots which migrate to the distal vasculature, and cause a stroke.
“Off-Pump” coronary artery bypass grafting, also called beating heart bypass grafting, takes place while the heart continues to beat, but a mechanical device may be used in an attempt to steady the surrounding vasculature, so that the practitioner can perform the graft. Off-pump coronary artery bypass surgery may reduce this risk. Frequently, because the graft must be performed on arteries in locations directly affected by the beating heart, stabilizing mechanisms are not thoroughly effective, and the practitioner must suture the graft while the graft is moving in conjunction with the heart beat, at least to some extent. Thus, the graft quality may be compromised.
Although, in a bypass surgery time is of the essence, the practitioner cannot rush through without thoroughly and precisely anastomising the graft(s). In conventional coronary artery bypass surgery, three critical determinates that affect the outcome of a bypass surgery are:
(1) time the patient spends on cardiopulmonary bypass,
(2) time the patient spends with a clamped aorta, and
(3) the quality of the anastomosis.
After an hour, the risk of patient morbidity is thought to increase perhaps due to the heart-lung machine degrading the quality of the blood as it is circulated through the systemic circulation. Bypass surgeries, however, often last three hours or longer. Moreover, where the aorta is clamped and blood therefore cannot pass through, the blocked blood is thought to cause additional issues.
Anastomosis is time-consuming. The average time for suturing one anastomosis is approximately fifteen to sixty minutes. An average CABG procedure is thought to involve approximately five anastomoses. Therefore, the average time for graft suturing exceeds the sixty-minute threshold for patient morbidity. Patients treated with conventional coronary surgery and placed on cardiopulmonary bypass would benefit from reducing the amount of time spent performing each anastomosis.
In “off pump” procedures where the heart remains beating, the difficulty of suturing an anastomosis graft on a moving surface of the heart may degrade the quality of such grafts completed on patients. An anastomosis differs from straight line suturing in that each suture has a different orientation that is based on its position around the cross-sectional circumference of the blood vessel graft. It can be appreciated that some of the sutures are easily made from on top of the conduit or blood vessel graft, while others are more difficult to complete as they are beneath the conduit. It can be further appreciated that performing such complex suturing procedures on a moving platform, such as the beating heart, further increases the difficulty associated with such suturing procedures. Improperly connecting blood vessel grafts to the patient may present substantial post-operative complications and/or increase operating room time spent correcting the improperly connected graft.
Accordingly, for surgical anastomosis, both practitioners and patients would benefit from faster procedures allowing patients to minimize procedure time, and simpler methods allowing reduced complexity and ease of use and higher quality anastomosis with fewer complications.